f8ec04e4a3
Any invalid/unsupported emoji flag sequence (whether using regional indicators or subdivision tags) gets replaced by the 'unknown flag' (PUA 0xFE28B), a flag with a blue question mark in the middle. The logic is mutated from the GSUB table of NotoColorEmoji.tmpl.ttx. We build these extra lookups using feaLib on an temporary empty font (that matches the glyph order of our destination CORLv1 font), then update our font's GSUB with them. The PUA for the unknown flag is then removed from the cmap, as it's no longer needed. It's also deleted from the CBDT NotoColorEmoji (see emoji_builder.py).
360 lines
12 KiB
Python
360 lines
12 KiB
Python
"""
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Post-nanoemoji processing of the Noto COLRv1 Emoji file.
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For now substantially based on copying from a correct bitmap build.
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"""
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from absl import app
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import functools
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from textwrap import dedent
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from fontTools.feaLib.builder import addOpenTypeFeaturesFromString
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from fontTools import ttLib
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from fontTools.ttLib.tables import _g_l_y_f as glyf
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from fontTools.ttLib.tables import otTables as ot
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import map_pua_emoji
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from nototools import add_vs_cmap
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from nototools import font_data
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from nototools import unicode_data
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from pathlib import Path
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from colrv1_add_soft_light_to_flags import add_soft_light_to_flags
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_OUTPUT_FILE = {
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"NotoColorEmoji-noflags.ttf": "fonts/Noto-COLRv1-noflags.ttf",
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"NotoColorEmoji.ttf": "fonts/Noto-COLRv1.ttf",
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}
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def _is_colrv1(font):
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return "COLR" in font and font["COLR"].version == 1
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def _is_cbdt(font):
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return "CBDT" in font
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def _is_compat_font(font):
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return "meta" in font and "Emji" in font["meta"].data
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def _copy_emojicompat_data(colr_font, cbdt_font):
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colr_font["meta"] = cbdt_font["meta"]
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def _set_name(name_table, nameID):
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name_table.getName(value, nameID, 3, 1, 0x409)
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def _set_name(name_table, nameID, value):
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name_table.setName(value, nameID, 3, 1, 0x409)
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def _copy_names(colr_font, cbdt_font):
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colr_font["name"] = cbdt_font["name"]
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name_table = colr_font["name"]
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assert all(
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(n.platformID, n.platEncID, n.langID) == (3, 1, 0x409) for n in name_table.names
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), "Should only have names Android uses"
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# Amendments
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_set_name(name_table, 10, "Color emoji font using COLRv1.")
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_set_name(name_table, 11, "https://github.com/googlefonts/noto-emoji")
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_set_name(name_table, 12, "https://github.com/googlefonts/noto-emoji")
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# CBDT build step: @$(VS_ADDER) -vs 2640 2642 2695 --dstdir '.' -o "$@-with-pua-varsel" "$@-with-pua"
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def _add_vs_cmap(colr_font):
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emoji_variants = unicode_data.get_unicode_emoji_variants() | {
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0x2640,
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0x2642,
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0x2695,
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}
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add_vs_cmap.modify_font("COLRv1 Emoji", colr_font, "emoji", emoji_variants)
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def _is_variation_selector_cmap_table(table):
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assert table.format in {4, 12, 14}
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return table.format == 14
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def _lookup_in_cmap(colr_font, codepoint):
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result = set()
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for table in colr_font["cmap"].tables:
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if _is_variation_selector_cmap_table(table):
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continue
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assert codepoint in table.cmap
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result.add(table.cmap[codepoint])
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assert len(result) == 1, f"Ambiguous mapping for {codepoint}: {result}"
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return next(iter(result))
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def _add_cmap_entries(colr_font, codepoint, glyph_name):
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for table in colr_font["cmap"].tables:
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if _is_variation_selector_cmap_table(table):
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continue
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if not _is_bmp(codepoint) and table.format == 4:
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continue
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table.cmap[codepoint] = glyph_name
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print(f"Map 0x{codepoint:04x} to {glyph_name}, format {table.format}")
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FLAG_TAGS = set(range(0xE0030, 0xE0039 + 1)) | set(range(0xE0061, 0xE007A + 1))
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CANCEL_TAG = 0xE007F
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def _map_missing_flag_tag_chars_to_empty_glyphs(colr_font):
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# Add all tag characters used in flags + cancel tag
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tag_cps = FLAG_TAGS | {CANCEL_TAG}
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# Anything already cmap'd is fine
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tag_cps -= set(_Cmap(colr_font).keys())
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# CBDT maps these to blank glyphs
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glyf_table = colr_font["glyf"]
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hmtx_table = colr_font["hmtx"]
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glyph_order_size = len(glyf_table.glyphOrder)
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for cp in tag_cps:
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print(f"Map 0x{cp:04x} to a blank glyf")
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glyph_name = f"u{cp:04X}"
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assert glyph_name not in glyf_table, f"{glyph_name} already in glyf"
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assert glyph_name not in hmtx_table.metrics, f"{glyph_name} already in hmtx"
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glyf_table[glyph_name] = glyf.Glyph()
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hmtx_table[glyph_name] = (0, 0)
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_add_cmap_entries(colr_font, cp, glyph_name)
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def _is_bmp(cp):
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return cp in range(0x0000, 0xFFFF + 1)
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def _ligaset_for_glyph(lookup_list, glyph_name):
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for lookup in lookup_list.Lookup:
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if lookup.LookupType != 4:
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continue
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for liga_set in lookup.SubTable:
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if glyph_name in liga_set.ligatures:
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return liga_set.ligatures[glyph_name]
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return None
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def _Cmap(ttfont):
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def _Reducer(acc, u):
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acc.update(u)
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return acc
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unicode_cmaps = (t.cmap for t in ttfont["cmap"].tables if t.isUnicode())
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return functools.reduce(_Reducer, unicode_cmaps, {})
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BLACK_FLAG = 0x1F3F4
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def _map_empty_flag_tag_to_black_flag(colr_font):
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# fontchain_lint wants direct support for empty flag tags
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# so map them to the default flag to match cbdt behavior
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# if the emoji font starts using extensions this code will require revision
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cmap = _Cmap(colr_font)
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black_flag_glyph = cmap[BLACK_FLAG]
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cancel_tag_glyph = cmap[CANCEL_TAG]
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lookup_list = colr_font["GSUB"].table.LookupList
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liga_set = _ligaset_for_glyph(lookup_list, black_flag_glyph)
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assert liga_set is not None, "There should be existing ligatures using black flag"
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# Map black flag + cancel tag to just black flag
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# Since this is the ligature set for black flag, component is just cancel tag
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# Since we only have one component its safe to put our rule at the front
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liga = ot.Ligature()
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liga.Component = [cancel_tag_glyph]
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liga.LigGlyph = black_flag_glyph
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liga_set.insert(0, liga)
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def _add_vertical_layout_tables(cbdt_font, colr_font):
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upem_scale = colr_font["head"].unitsPerEm / cbdt_font["head"].unitsPerEm
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vhea = colr_font["vhea"] = ttLib.newTable("vhea")
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vhea.tableVersion = 0x00010000
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vhea.ascent = round(cbdt_font["vhea"].ascent * upem_scale)
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vhea.descent = round(cbdt_font["vhea"].descent * upem_scale)
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vhea.lineGap = 0
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# most of the stuff below is recalculated by the compiler, but still needs to be
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# initialized... ¯\_(ツ)_/¯
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vhea.advanceHeightMax = 0
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vhea.minTopSideBearing = 0
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vhea.minBottomSideBearing = 0
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vhea.yMaxExtent = 0
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vhea.caretSlopeRise = 0
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vhea.caretSlopeRun = 0
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vhea.caretOffset = 0
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vhea.reserved0 = 0
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vhea.reserved1 = 0
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vhea.reserved2 = 0
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vhea.reserved3 = 0
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vhea.reserved4 = 0
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vhea.metricDataFormat = 0
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vhea.numberOfVMetrics = 0
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# emoji font is monospaced -- except for an odd uni0000 (NULL) glyph which happens
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# to have height=0; but colrv1 font doesn't have that anyway, so I just skip it
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cbdt_heights = set(h for h, _ in cbdt_font["vmtx"].metrics.values() if h != 0)
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assert len(cbdt_heights) == 1, "NotoColorEmoji CBDT font should be monospaced!"
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height = round(cbdt_heights.pop() * upem_scale)
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vmtx = colr_font["vmtx"] = ttLib.newTable("vmtx")
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vmtx.metrics = {}
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for gn in colr_font.getGlyphOrder():
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vmtx.metrics[gn] = height, 0
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UNKNOWN_FLAG_PUA = 0xFE82B
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REGIONAL_INDICATORS = set(range(0x1F1E6, 0x1F1FF + 1))
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def _add_fallback_subs_for_unknown_flags(colr_font):
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"""Add GSUB lookups to replace unsupported flag sequences with the 'unknown flag'.
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In order to locate the unknown flag, the glyph must be mapped to 0xFE82B PUA code;
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the latter is removed from the cmap table after the GSUB has been updated.
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"""
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cmap = _Cmap(colr_font)
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unknown_flag = cmap[UNKNOWN_FLAG_PUA]
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black_flag = cmap[BLACK_FLAG]
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cancel_tag = cmap[CANCEL_TAG]
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flag_tags = sorted(cmap[cp] for cp in FLAG_TAGS)
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regional_indicators = sorted(cmap[cp] for cp in REGIONAL_INDICATORS)
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classes = dedent(
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f"""\
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@FLAG_TAGS = [{" ".join(flag_tags)}];
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@REGIONAL_INDICATORS = [{" ".join(regional_indicators)}];
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@UNKNOWN_FLAG = [{" ".join([unknown_flag] * len(regional_indicators))}];
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"""
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)
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lookups = (
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# the first lookup is a dummy that stands for the emoji sequences ligatures
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# from the destination font; we only use it to ensure the lookup indices match.
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# We can't leave it empty otherwise feaLib optimizes it away.
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dedent(
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f"""\
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lookup placeholder {{
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sub {unknown_flag} {unknown_flag} by {unknown_flag};
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}} placeholder;
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"""
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)
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+ "\n".join(
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["lookup delete_glyph {"]
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+ [f" sub {g} by NULL;" for g in sorted(regional_indicators + flag_tags)]
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+ ["} delete_glyph;"]
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)
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+ "\n"
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+ dedent(
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"""\
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lookup replace_with_unknown_flag {
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sub @REGIONAL_INDICATORS by @UNKNOWN_FLAG;
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} replace_with_unknown_flag;
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"""
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)
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)
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features = (
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"languagesystem DFLT dflt;\n"
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+ classes
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+ lookups
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+ dedent(
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f"""\
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feature ccmp {{
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lookup placeholder;
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sub {black_flag} @FLAG_TAGS' lookup delete_glyph;
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sub {black_flag} {cancel_tag} by {unknown_flag};
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sub @REGIONAL_INDICATORS' lookup replace_with_unknown_flag
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@REGIONAL_INDICATORS' lookup delete_glyph;
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}} ccmp;
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"""
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)
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)
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# feaLib always builds a new GSUB table (can't update one in place) so we have to
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# use an empty TTFont and then update our GSUB with the newly built lookups
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temp_font = ttLib.TTFont()
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temp_font.setGlyphOrder(colr_font.getGlyphOrder())
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addOpenTypeFeaturesFromString(temp_font, features)
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temp_gsub = temp_font["GSUB"].table
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# sanity check
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assert len(temp_gsub.FeatureList.FeatureRecord) == 1
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assert temp_gsub.FeatureList.FeatureRecord[0].FeatureTag == "ccmp"
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temp_ccmp = temp_gsub.FeatureList.FeatureRecord[0].Feature
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colr_gsub = colr_font["GSUB"].table
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ccmps = [
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r.Feature for r in colr_gsub.FeatureList.FeatureRecord if r.FeatureTag == "ccmp"
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]
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assert len(ccmps) == 1, f"expected only 1 'ccmp' feature record, found {len(ccmps)}"
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colr_ccmp = ccmps[0]
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colr_lookups = colr_gsub.LookupList.Lookup
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assert (
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len(colr_lookups) == 1
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), f"expected only 1 lookup in COLRv1's GSUB.LookupList, found {len(colr_lookups)}"
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assert (
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colr_lookups[0].LookupType == 4
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), f"expected Lookup[0] of type 4 in COLRv1, found {colr_lookups[0].LookupType}"
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colr_lookups.extend(temp_gsub.LookupList.Lookup[1:])
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colr_gsub.LookupList.LookupCount = len(colr_lookups)
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colr_ccmp.LookupListIndex = temp_ccmp.LookupListIndex
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colr_ccmp.LookupCount = len(colr_ccmp.LookupListIndex)
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# get rid of the Unknown Flag private codepoint as no longer needed
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font_data.delete_from_cmap(colr_font, [UNKNOWN_FLAG_PUA])
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def main(argv):
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if len(argv) != 3:
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raise ValueError(
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"Must have two args, a COLRv1 font and a CBDT emojicompat font"
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)
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colr_file = Path(argv[1])
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assert colr_file.is_file()
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assert colr_file.name in _OUTPUT_FILE
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colr_font = ttLib.TTFont(colr_file)
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if not _is_colrv1(colr_font):
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raise ValueError("First arg must be a COLRv1 font")
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cbdt_file = Path(argv[2])
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assert cbdt_file.is_file()
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cbdt_font = ttLib.TTFont(cbdt_file)
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if not _is_cbdt(cbdt_font) or not _is_compat_font(cbdt_font):
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raise ValueError("Second arg must be a CBDT emojicompat font")
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print(f"COLR {colr_file.absolute()}")
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print(f"CBDT {cbdt_file.absolute()}")
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_copy_emojicompat_data(colr_font, cbdt_font)
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_copy_names(colr_font, cbdt_font)
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# CBDT build step: @$(PYTHON) $(PUA_ADDER) "$@" "$@-with-pua"
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map_pua_emoji.add_pua_cmap_to_font(colr_font)
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_add_vs_cmap(colr_font)
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_map_missing_flag_tag_chars_to_empty_glyphs(colr_font)
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_map_empty_flag_tag_to_black_flag(colr_font)
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add_soft_light_to_flags(colr_font)
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_add_vertical_layout_tables(cbdt_font, colr_font)
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_add_fallback_subs_for_unknown_flags(colr_font)
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out_file = Path(_OUTPUT_FILE[colr_file.name]).absolute()
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print("Writing", out_file)
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colr_font.save(out_file)
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if __name__ == "__main__":
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app.run(main)
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